The overall objective of documenting the regulation of glycolysis in brain is approached from two aspects: a detailed study of the protein and or phospholipid factors required for the binding of hexokinase to the mitochondrial membrane, and a study of the partitioning of hexokinase, phosphoglucose isomerase, phosphofructokinase and creatine kinase between mitochondria and cytosol as a function of the energy status of nerve cells. The structural aspects of the investigation are based on our previous observation that brain hexokinase, eluted from mitochondria by glucose-6-phosphate, is capable of rebinding to mitochondria, while the same preparation, purified by DEAE cellulose chromatography, is not capable of rebinding. Furthermore, the two forms have different apparent molecular weights as determined by SDS polyacrylamide electrophoresis. Experiments are proposed which will allow us to determine the nature of the binding factor(s) which are lost upon DEAE cellulose chromatography. For the functional aspects of the investigation, isolated neuronal perikarya will be used as a model of intact brain. The energy status of the neuronal soma will be varied in an accurately controlled manner and the subcellular distribution of the four enzymes listed above correlated with the energy status as determined by the rate of oxygen uptake following glucose addition and by the concentrations of ATP, ADP, AMP and creatine phosphate.